/**
 * Copyright 2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * 	http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.xume.raob.extensions.jpa;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;

import org.xume.raob.api.ObjectBuilder;

/**
 * @author Johan Siebens
 */
public final class JpaBuilder {

	public static <T> T persit(ObjectBuilder<T> builder, Using using) {
		T entity = builder.build();
		EntityManager em = using.get();

		EntityTransaction transaction = em.getTransaction();
		boolean error = false;
		try {
			transaction.begin();
			em.persist(entity);
			return entity;
		} catch (Exception e) {
			error = true;
			throw new JpaBuilderException("Failed to persist entity", e);
		} finally {
			if (!error) {
				transaction.commit();
			} else {
				transaction.rollback();
			}
		}
	}

	public static Using using(final EntityManager entityManager) {
		return new Using() {

			public EntityManager get() {
				return entityManager;
			}

		};
	}

	public static Using using(final EntityManagerFactory entityManagerFactory) {
		return new Using() {

			public EntityManager get() {
				return entityManagerFactory.createEntityManager();
			}

		};
	}

	private JpaBuilder() {
	}

	public interface Using {

		EntityManager get();

	}

}
